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COSMAC VIP

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COSMAC VIP
DeveloperJoseph Weisbecker
ManufacturerRCA
Typemicrocomputer
Release date1977; 47 years ago (1977)
Introductory priceUS$275 (Kit)
Operating system4-kilobit (512-byte) in ROM
CPURCA 1802 processor
Memory2 KB RAM (Expandable to 4 KB on board, and 32 KB via an expansion slot)
Storagecassette tape
DisplayCDP1861/CDP1864 video display chip
Soundspeaker
Power5V DC CDP18S023 power supply @ 600 mA

The COSMAC VIP (1977) was an early microcomputer that was aimed at video games. Essentially, it was a COSMAC ELF with a supplementary CDP1861/CDP1864 video display chip. For a price of US$275, it could be purchased from RCA by mail order. It came in kit form, and had to be assembled. Its dimensions were 22 x 28 cm, and it had a RCA 1802 processor; along with a crystal clock operating at 1.76 MHz.[a] It had 2 KB (2048 bytes) of RAM, which could be expanded to 4 KB on board, and 32 KB via an expansion slot. Its 5V DC CDP18S023 power supply had an output of 600 mA. I/O ports could be added to connect to sensors, interface relays, an ASCII keyboard, or a printer.

The machine connected to either a video monitor or to a TV with video input or by means of an external RF modulator. The VIP used a CDP1861/CDP1864 video display chip to generate the video output, and sound could be played using its integrated speaker. It had a 100 bytes per second cassette tape interface as well. Programs could be loaded into RAM from tapes, and vice versa. It also had a hex keyboard for input, which had 16 keys spanning the hex digits 0 to F. LED indicators were used to display power status and tape input; a third LED along with an on-board beeper were activated by the CPU's 1-bit "Q" register. A run/reset switch was used to start user programs or the operating system, respectively.

A simple 4-kilobit (512-byte) operating system was built into its ROM. It allowed one to type in programs using its hex keyboard, show memory contents on its display (step through the bytes of RAM), and view the values of the processor registers. The ROM monitor was accessed by holding the "C" key while switching from Reset to Run. The COSMAC VIP was shipped with 20 video games, which were programmed in CHIP-8. CHIP-8 was an early interpreted programming language that was used on this machine and other early microcomputers, such as the Telmac 1800. The video games that were provided came as a list of instructions which had to be typed in by the user.

The COSMAC VIP was created by Joseph Weisbecker of the RCA Laboratories in New Jersey. His daughter Joyce created some of the games included with it.[1] RCA sold a $39 version of Tiny BASIC on an expansion board.[2]

A VIP II version was designed, bundling the VIP with several expansion cards and selling it in fully assembled form. Marketing materials from 1979 refer to a 1980 release, but this never occurred. Several years later the VIP II was equipped with a ROM containing a terminal program and sold as a portable terminal device under the name RCA VP 3000.

Notes

  1. ^ The clock speed of many computers of the era was some multiple or factor of the base NTSC frequency of 3.579545 MHz (315M/88), derived either from a common TV colorburst crystal of the same frequency, or a similarly commoditized direct multiple such as 14.318 MHz; in many early machines, it was used straight, or divided by 2 or 4, to give 1.790 or 0.895 MHz, pulling close to the maximum speed out of common 4, 2 or 1 MHz rated chips whilst leaving a little overhead for faulty parts, whilst making interfacing with NTSC televisions and producing both correct syncs and some form of colour relatively simple. The VIP is somewhat unique in not using a standard NTSC crystal, but a slight deviation, to 1.76064 MHz - rather slower than the 1802 CPU's rated 3.2 MHz - in order to match with the even simpler-than-usual sync timing structure of the extremely cheap, but also extremely rudimentary "Pixie" video generator chip, allow use of a single crystal to run both processor and video (not only cost-saving, but also necessary for properly synchronised operation, given the system architecture where the video chip uses the CPU's built-in DMA functionality to receive data from RAM). It also, for reasons best known to the COSMAC designers, prefers a strict adherence to the 60.00 Hz frame timing of monochrome, NTSC-compatible 525-line televisions and monitors, even though this enforced a line-scan rate of 15.72 kHz that was a good bit lower than both the monochrome and 1001/1000ths-slower color standards. Possibly they mistook the nominal rates of the standard as being maxima, rather than means with a certain amount of deviation allowable either side, a truth that most other early computers took advantage of to produce still-eminently-TV-compatible signals of approximately - and usually somewhat higher than - 59.94 Hz and 15.734 kHz, using standard NTSC crystals and still reasonably simple circuitry.

References

  1. ^ Edwards, Benj (2017-10-27). "Rediscovering History's Lost First Female Video Game Designer". Fast Company. Retrieved 2017-10-27.
  2. ^ Dolce, Larry (April 1980). "RCA's VIP Tiny BASIC". Kilobaud. p. 111. Retrieved 23 June 2014.
Notes
  • The December 1978 BYTE magazine featured an article on CHIP-8 ("An Easy Programming System") as well as an advertisement for the VIP system.
  • The May 1977 Dr. Dobb's Journal reprinted an article by Joseph Weisbecker ("A Practical, Low-cost, Home/School Microprocessor System") describing the design philosophies and economies that went into designing the VIP—which was at the time called FRED ("Flexible Recreational and Educational Device"). That article originally appeared in the August 1974 IEEE "Computer" magazine.
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